How do I get Blender to export a single mesh instead of multiple meshes?
Like FFeller mentioned, select all the objects, right-click, and press Join. Make sure you shift click one of the objects so that at least one of them is selected, otherwise it is impossible to join them.
In the FBX export screen, there will also be an option to export only &quot;Selected Objects&quot;, or just the &quot;Active Collection&quot;.
Select the objects and collections you have to export, and tick both of those. If are still having problems, maybe export the objects as OBJ and everything else as FBX.